Several Possible Explanations Accounts for the Pay Differential Between Women

Several possible explanations accounts for the pay differential between women and men. Which of the following statements is NOT one of these reasons.

A) Men tend to work longer hours,which boosts pay.
B) Women are more likely to be unionized,so they have more benefits,but lower pay than do men.
C) Labor market segmentation disadvantages women.
D) Discrimination occurs against women.